In conventional inverted microscopes, such as those disclosed in U.S. Pat. Nos. 4,210,384 (Meyer et al.) and 4,685,776 (Inoue et al.), the light rays passing through the microscope lens are directed perpendicularly downward from the specimen and then deflected from this downward path along at least one of two horizontal ray paths, a first one of these ray paths being again deflected upwardly in the direction of the viewer, while the second of these paths continues horizontally to an auxiliary image port used for the recording of the image by a camera or video recorder.
This conventional organization of the ray paths requires that the microscope's specimen stage be positioned relatively high because a large amount of space is required beneath the microscope's lens for beam-splitting prisms, some of which are adjustable. Also, the second ray path to the camera port must be positioned at a certain minimum height above the bottom of the microscope housing in order to permit the use of a recording camera with an automatic-winder housing. Since the second ray path to the auxiliary camera port is positioned below the first ray path to the viewer, and since both of these ray paths are positioned below the lens, both the lens turret and the specimen stage must be positioned quite high on the microscope's housing. This prior art arrangement is ergonomically unsatisfactory, because it does not permit the operator to manipulate the specimen with his or her arms supported.
U.S. Pat. No. 4,685,776 has positioned the plane of the ray path to the camera port above the ray path to the viewer. However, this requires that the two ray paths intersect a second time, thus resulting in design restrictions. Further, this just-described prior art arrangement deflects the light path from the specimen to the viewer up to five times, making the apparatus relatively complex and reducing image quality.
In a company brochure entitled "Nikon Epiphot", Nippon Kogaku KK discloses an inverted microscope with integrated light ray paths in which the path for the viewing rays is deflected by a single reflection, from the downwardly directed combined light path from the microscope's lens, diagonally upward to the viewer. This diagonally-upward path of the viewing rays is identical to the angle at which the operator looks into the eyepieces of the microscope.
However, this Nikon arrangement still requires a relatively high stage area because, as is true of the other two conventional arrangements discussed above, the second path to the auxiliary port is positioned below the prism which splits the combined rays from the microscope's lens into the viewing and auxiliary paths. Further, it is often considered desirable to provide additional auxiliary image ports for recording or measuring equipment larger and/or heavier than a simple camera, such additional image ports usually being arranged with a vertical optical axis so that the weight of the auxiliary equipment can be directly supported by the microscope housing. However, with the just-described Nikon arrangement, it is complex to deflect light from the diagonally-upward path of viewing rays to any such additional image ports, particularly if it is also desired to releasably attach the additional port and/or the viewer's binocular tube to the microscope housing by means of one or more interchangeable tubes.
An inverted microscope is also disclosed in U.S. Pat. No. 4,770,520 in which the downwardly directed light path from the microscope's lens is deflected, by a single reflection, diagonally upward to the viewer. In the diagonally upward light path, a first intermediate image is formed which is imaged by a zoom lens system into the second intermediate image plane within the viewer's oculars. A switchable mirror is provided between the zoom lens system and the oculars. Using this switchable mirror, the light path can be deflected to a horizontal camera port below the oculars.
With this just-described prior art microscope, it is not possible to direct the light to the oculars and to the camera at the same time. Further, since the imaging conditions in the viewing ray path and in the camera ray path are the same, the image size in the camera is the same as the image size in the viewer's oculars, the latter image normally being smaller than the format of the photographic film. Finally, this known system has a further disadvantage: The binocular tube is not interchangeable; and even if interchangeable binocular tubes would be added to this structure, only such tubes could be used which have the same optical path length from their interface plane to the second intermediate image plane.
Our invention is a novel arrangement for an inverted microscope with a simple and compact construction which minimizes the number of deflections in the path of the viewing rays, provides ample room at the auxiliary port to permit use of a recording camera having an automatic-rewind housing, and still locates the specimen stage at a relatively low, ergonomically-appropriate position.
Further, the invention provides additional auxiliary ports arranged in relatively simple interchangeable tubes which can be releasably attached to the housing by means which are not subject to sensitive manufacturing tolerances.